You know an inteface is intuitive enough for launch to public only when a three-year-old can use it without problems. :)
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Ilari KajasteJul 11 '13 at 6:33

4

@IlariKajaste The number of times I have seen toddlers helping out their parents use and app, I just hope this were true.
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rk.Jul 11 '13 at 12:29

I always think a checkout process is good if one can make impulse purchases while under the influence of alcohol, though my bank balance does not agree.
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Toni LeighJul 15 '13 at 22:03

I believe that there are some common software interface features that started out as accessibility features for either vision impaired or people who are unable to use a mouse, but I can't think of the actual references.
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Michael LaiJul 18 '13 at 4:23

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As the brief of the question has been broadened, it's now worth mentioning the concept of Universal Design ( Designing for people with 'sub-optimal' human performance) en.wikipedia.org/wiki/Universal_design
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PhillipWJul 22 '13 at 11:09

I would say that considering people who are impaired or intoxicated is always useful. I think the implication is quite clear: if impaired persons are able to use an interface with ease, then unimpaired persons should also find it easy to use.

There are a few examples of interfaces which are used by a high number of drunk people. Pub quiz machines and karaoke machines spring to mind. In these cases, it is imperative that the interface at least considers the effects of drunkenness (e.g. blurred vision, poor hand-eye coordination, etc).

While it sounds interesting, you only need to do this if your target demographic is in this population. Car manufacturers might want to do some drunk testing to see how they can prevent drinking and driving, factory owners might want to test the effect of fatigue of machine operations, etc.

I agree that it makes sense to test impaired users for things that might or shouldn't be used by such people. A taxi-hailing mobile app or a car dashboard with a pre-drive cognitive test are examples. Even then impaired-user testing is not totally practical or ethical. You have to round up drugged/drunk/tired people or induce them until they are that way.

It's a slippery slope to step onto unless you carry out testing like real scientific experiments with ethical guidelines like informed consent and voluntary continuation. For user-experience testing, it's best to create realistic scenarios (ie, real objectives and obstacles) without altering the user. You're testing the product, not the user.

If you are creating an interface that in certain scenarios involves drunk/ tired/ drugged people using it, then by all means you should! For example : Hire a cab service mobile apps can be tested for effectiveness to call a cab especially when they are not in a position to drive.

Safety related apps that involve users not being able to think before they do something.

If your target demographic does not involve such users then you can consider it, but understand that testing with a drunk/ tired / drugged person does not mean that it gives accurate results on how the user experience is. Each person's mental reaction in such a state is quite different from the next person. You may end up with skewed results and frankly it might do you more harm than help.

This is highly possible. I use both usability subjective testing and neuro-imaging (EEG) tools to test user experience with different speech stimulus (interfaces). From subjective studies, we may not get accurate sense, but I learnt from EEG brain wave analysis that certain persons were really tired and drowsy during test and others were very alert and engaged. In short, tired, and/or drugged people may skew our results.